JPH02235457A - Communication network - Google Patents

Abstract

PURPOSE: To add and delete individual master node to and from a network by incorporating processors in a plurality of master nodes connected to a single data bus and generating signals impressed upon the data bus from individual nodes. CONSTITUTION: Nodes 12-15 and a communication master node 16 are provided and the nodes 12-15 and 16 are connected to a data bus. Such a node as the node 12 or 16 is provided with a microprocessor 19 and the microprocessor 19 is physically realized in the form of instructions for physically generating various signals impressed upon the data bus. The instructions are stored in an instruction memory 26 and each master node transmits messages and updates its own succeeding node address. The communication mater node 16 updates or maintains an action master list and, at the same time, simultaneously communicates the action master list with the other master nodes 12, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION PRIOR ART AND PROBLEMS SOLVED BY THE INVENTION In certain systems that include a large number of spaced apart components or devices and may take a variety of different forms, It would be useful if these individual components X could be controlled via one network. In that case, each component of the system is assigned a station, or node, which has the ability to communicate with other nodes in the network. This allows the operation of the individual components of the system to be coordinated so that they can function effectively as one system at low cost. The individual components perform functions in the manufacturing process or, in the actual case where the system described here is applied, in heating, ventilation and air conditioning in commercial and industrial buildings. The intended purpose may be to do so.

To support such systems in a large number of different configurations, it is preferred that the network controlling the system has the ability to be configured flexibly. Furthermore, such a system may be changed from time to time to a different configuration, and at the same time it is very advantageous if the control network can be easily adapted to the configuration of the system. It is also desirable to ensure that failures of individual nodes in the network do not cause the entire system to shut down. Finally, it would be desirable to be able to connect the individual nodes of the control network to each other in order to exchange information between the nodes via a single conductor with a return circuit or via a pair of conductors.

The nine conditions listed after R represent sequential communication.

There are currently a number of temporal networks available that can function in this manner.

In one, a particular node is used as a master, coordinating communications between itself and other nodes via a data bus. After all, there are also types of networks that include several master nodes of roughly equal capacity that can communicate with each other via a data bus. Among the latter systems, those that have been implemented successfully are those that utilize tokens that are passed from one master node to the next in the network. Node,
Next to performing a transmission over the data bus, one must possess the token. Since only sequential communication takes place, it is necessary to ensure that only one node is transmitting at any given time to prevent interference between messages occurring simultaneously.

71) for controlling or specifying which nodes can transmit over the data bus at a given time;
More specifically, using token messages, an individual master node can designate the next node that is allowed to transmit by giving it a token message. To do this,
Each master node must have a unique network address necessary to send token messages to the desired node. Special. If a given node has no messages at all when it receives the token message it wishes to send, it simply
It simply passes the token message to the next designated node. This way, any node will eventually have the opportunity to send a signal over the data bus if there is any other master node sending a token to it.

The token message first includes a token passing code that identifies the message as a token message;
Second, the token message is sent so it has a predetermined unique formant containing the successor node address, which is the network address of the node that should become active next.

Sending a token message signals that the master node sending the token message is terminating its active state. Each master node must include a successor node address register in which the successor node address is stored.

In a network that includes a single master node and many slave nodes, the master node
Each slave node stores a list of addresses specifying the order in which it receives tokens. In this type of network, the master node must take control of the network as each of the other nodes completes its activity.

Each of these schemes lacks several capabilities that are desired when considering network flexibility and reliability. For example, in a master-slave type network, if the master node fails for some reason, the entire network will fail accordingly. In a multiple master token passing network, it is difficult to change the exact order in which nodes are allowed to transmit along the communication path. That is, a considerable amount of time may elapse between the time an event requiring immediate attention occurs and the time a particular node is allowed to transmit in hopes of receiving the token again. In some situations, it may be necessary to have nodes possess tokens and have the opportunity to send them more frequently than this. Therefore, the network cannot function with the physical system with the desired efficiency and effectiveness.

There are several network configurations that solve either of these problems. For example, U.S. Patent No. i,566,0
In the network hardware described in No. 97, a node with a higher priority message is terminated by transmitting a command to the node-crossing station with a lower priority message to terminate transmission. Nodes with lower priority messages can be prioritized. U.S. Patent No. 4. No. 491,946 has a predetermined strict order in which tokens pass from one node to another, but it is easy to add nodes to or remove nodes from the network. A token passing network is described. Other U.S. patents that include the ability to pass tokens through nodes within a communications network include No. 4,663.74.
No. 8, No. 4,674,086, No. 4.566, 09
No. 7 and No. 4,511,958.

Another problem relates to the procedures for adding or removing individual nodes from the network. According to one of the procedures, each individual node cycles through all the inactive network addresses, each one larger than the individual node's own address and smaller than the successor node address for the associated node. Detects the presence of new nodes in the network by maintaining a karanta. This method has the advantage of simplicity; however, if the number of active nodes in the network is small compared to its maximum allowed size, the network address of a new node is generated by increments, Many token cycles are required before the node receives the token for the first time.

[Means for solving problems]

The present invention solves many of the above problems with a system that includes multiple master nodes that have the ability to send and receive tokens in a conventional manner. There is also one master node (communication master) that maintains an active master list that holds the network address of each master node. Whenever for some reason it becomes necessary to rearrange the order in which token messages are passed by all master nodes, the communication master broadcasts the active master list in the form of messages with a unique identification format. . This message provides a signal over the data bus encoding the active master list and essentially contains all of the contents of the active master list stored in the address memory of the communicating master node. 1st
Each master node other than the master node includes means for receiving an active master list message via a data bus from a communicating master node, and further determines the presence or absence of the master list message by detecting the presence or absence of a unique identification format of the master list message. and means for retrieving, from the master list, a network address subsequent to the network address of the concerned master note in response to the command, and storing the master node address so retrieved in a successor node address register of the concerned master made. including means to do so.

To make this scheme work, it is necessary to identify the newly added master node as such in the network. One possible method is to provide a dead space in conjunction with the transmission of one token message or at the end of one complete cycle through the node. This often has the disadvantage of being time consuming and
If two nodes are added between the two deadheads 9, a collision will occur when both nodes try to identify themselves to the communications master. Another method generates individual signals directed to every legal address in the network. Although effective, this is somewhat time consuming. The preferred solution is a binary search scheme that addresses nodes rather than directing individual queries to every valid address, allowing nodes to respond individually. Without going into details here, suffice it to say that the communication master sends a number of signals that are sent to different groups of nodes that are newly added to the network. After several iterations, it is necessary to detect whether no reply signal has occurred, one reply signal has been fired, or a collision of reply signals has occurred, and all newly added nodes are separated and Those individual networks will be identified. Once the communication master has the address of the newly added i-star node, it can update the active master list by inserting the new master node's network address into the active master list.

Accordingly, one object of the present invention is to add individual master nodes to the network and to add individual master nodes to the network without requiring external intervention to reset the network. It is possible to remove a star node from the network.

A second objective is to allow each master node to immediately determine its successor master node upon system startup or restart.

Another objective is to reduce data bus traffic when updating subsequent masters in the network.

Yet another objective is to define a tolerance measure for dropping individual master nodes from the network.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Referring first to FIG. 1, a communication data bus having a pair of conductors 810 and 11 is shown in FIG. These conductors typically carry differential signals, with the waveform of one conductor being a complete inversion of the waveform of the other conductor. Preferably, the conductors 10 and 11 form twisted bare wires.

That is, the conductors are physically twisted so that they are generally subject to the same noise events.

Since the signal is sensed differentially at each node, such external noise essentially disappears.

Although it is possible to use a single conductor with a ground return to form the second conductor, this is not preferred due to the lack of noise immunity. Nodes 12-15 and one first node, ie a communication master node 16, are provided, all of which are connected to a data bus.

FIG. 2 shows a typical node, such as node 12 or 16 of FIG. 1, and the individual hardware blocks that make it up. A preferable example of the construction node is:
Motoro1 with various block functions illustrated
It includes a standard microprocessor 19, such as a M6803. It should be noted that the present invention is physically realized in the form of instructions that are introduced into this microprocessor 19 and physically generate various signals that are applied to the Elidata bus at the individual nodes. These instructions are each stored in the instruction memory 26 and have the essential functions shown in the figures for the present invention. Each master node can send messages and update its own successor node addresses. The communicating master node 16 (FIG. 1) must also update or maintain an active master list and broadcast the active master list to other master nodes 12 and so on.

data memory 20, an input/output interface 22 which normally forms part of a microprocessor;
．． Instruction processor 21 and instruction memory 26 are also all included in the microprocessor. Input/output interface 22 coordinates the transfer of data between data memory 20 and serial/parallel converter 23 under the control of instruction processor 21 .

Serial/parallel converter 23 converts the next 8-bit byte information provided by input/output interface 22 and converts the information from input/output interface 22 into serial data provided to transmitter driver 24 . Transmitter driver 24
to conductors 10 and 11 that transmit information to other nodes,
Generate the actual voltage waveform. Information on leads 10 and 11 is also received by receiver amplifier 25. Receiver amplifier 25 provides a signal to serial/parallel converter 23 that can be converted into the 8-bit bytes required for acceptance by input/output interface 22 . The input/output interface 22 then causes the information from the serial/parallel converter 23 to be stored in the appropriate storage location in the data memory 20 under the control of the instruction processor 21.

FIG. 3 shows the structure of each message generated by each node. There are two formats shown. Each activity master message is preceded by a ``bu'' amble that announces the start of the message. The jin preamble contains a generalized description of the message that follows, and the structure of the preamble is not important at this point.

The body of the message immediately follows the preamble and includes a series of bits that uniquely represent the purpose of the message and the type of response to be elicited from the node or nodes responding to the message. ) segment.

DESTINATION ADDRESS segment and SOURCE ADDRESS
The (transfer source address) segment represents the address to which the message is sent and the node address of the sending node. EXTΔSION-TYPE (
Extension type) segments further limit the purpose of the message, but do not need to be considered. DATA
The (data) segment contains the body of the message and, depending on its purpose, may contain any number of different information packets. CHECKSUM (checksum) contains some kind of redundant information that allows the receiving node to determine the accuracy of the message transmission and, in some cases, even to correct the message if there are only a small number of errors. . The responses generated to active master messages are similar to active master messages, except that no destination address is specified.

FIG. 4 is a functional block diagram of a portion of each node incorporating the present invention. The functions enclosed by the dashed rectangle 41 include, among the various master nodes 12, etc., several functions associated with storing the active master list and maintaining that list and propagating the list to other master nodes. This is a function given only to the communication master node 16 that executes the function. Communication interface 40 includes an input/output interface 22, a serial/parallel converter 23, a transmitter driver 24, and a receiver amplifier 25 as shown in FIG. Communication interface 40 includes multiplexers that select individual inputs and outputs as they occur. In reality, the functionality of this multiplexer is
It is executed in accordance with the instructions retrieved from the instruction memory 26 and executed by the instruction processor 21.

It is convenient to begin this discussion with the common master function, which interacts with the communication master function in form 41. Common master functions include the processing of token messages, token acknowledgment messages, activity master list broadcast messages, and activity master list update timing messages transmitted by other nodes; generation of a list update message; and clearing of the activity master list update flag. It should be noted that each of the functions shown in FIG. . Typically, the various registers shown are physically Fi, data memory 2
0 various memory locations.

Timing considerations typically have to be taken into account if the displayed functionality is to achieve the desired aforementioned objectives. Generally, the timing of such considerations is implicit in this discussion. In addition, regarding various related timing conditions and sequence conditions,
The implied timing lt= will also be mentioned.

The node address register 42 is the communication interface 4
0, the mask of which that particular node address register 42 is a part receives the actual numerical network address assigned to the node. The contents of the node address register 42 are set by the user of the network, either before or immediately after the node itself is attached to the data bus conductors 10 and 11. The node address stored in the node address register 42 can only be changed manually in this network.

Token messages are transmitted over the data bus for the purpose of designating another node 12, etc. as active. The winter token message is sent to the token message register 43 by the communication interface 4o at each node (except the nine nodes that sent the message). Communication interface 40 identifies the token message by a unique identification format, which is a unique bint pattern in the MESSAGE TYPE segment (see FIG. 3), when sending the token message to token message register 43. In each token message, DESTrNAT
The ION ADDRESS segment contains the successor node address, which is the address of the next node 12, etc., to become active. Comparison element 46 compares the contents of node address register 42 and the DESTINATION of the token message stored in token message register 43.
ADDRF. and the subsequent node address of the SS segment. When these two addresses are equal, it is
It represents a case in which a master node that is assigned the same node address can become active as indicated by the start transmit activity block 61.

A master node whose comparison result is negative remains inactive, ie, quiescent.

There are several other activities that occur when the result of the comparison performed on comparison element 46 is positive. These activities include issuing a token acknowledgment message and clearing the activity master list update flag. These two activities will be explained later to provide a more logical structure to the explanation. Additionally, there is an active master list function activated by this comparison, which is discussed as part of the description of communication master node 16.

The event that a token message is sent to the master node causes the master node to make its network address the successor node address for another node, or in rare cases, before the master node can become active. However, it is necessary to generate that address when a token message addressed to another node is not acknowledged for some reason. One way to achieve this objective is when a node's network address is entered into an active master list that is permanently stored in one node 16 (FIG. 1) that acts as a communications master among the nodes. It is. In FIG. 4, the active master list fixed file is shown as part of the communications master function subsystem 41. Although there are several ways to arrange the active master list, it is preferred to simply list all of the master nodes to be activated in the sequence in which the master nodes become active. In this method,
Immediately following the network address N in the active master list is the network address of the node to which the ERI token message is to be sent to the node with that network address N. In the following, it is assumed that the activity master list is arranged in this manner.

The processing within the individual master nodes 12, etc. associated with the active master list function is the next logical consideration. For purposes of this discussion, it is noted that, from time to time, active master list messages are broadcast directly by the communication master node 16 via the data bus and received by the respective communication interfaces 40 via conductors 10 and 11t. It is sufficient if you understand. The activity master list broadcast message generator 67 includes a unique identification format in the MESSAGE-TYPE segment of the activity master list message, which indicates that the activity master list has a defined function for the purpose of temporary storage. The communication interface 40 of each master node 12, etc. is arranged to temporarily store the file represented by block 45. In this preferred embodiment, data memory 20 performs the file 450 function. It is entirely possible to have only two of the addresses included in the active master list message stored in file 45 at any given moment. Friend, during the transmission of the activity master list message, this file contains the network address of the master node of which it is a part and the token message (7) DESTINATION ADDR which is transmitted to the associated master node 13 and so on.
The ESS only needs to receive and store the network address associated with that square 1-/-} as the subsequent node address to be introduced. and retrieves the network address of that master node to be stored in the token message provided by the master node.
This so-called successor node address is . Activity Master List Processor 5 0K! C, stored in the subsequent node address register 51.

The functionality shown as token message generator element 53 serves as a token message generated by the particular master node K concerned and stored by other master nodes in their own token message registers 43. Specifies the format of the Qun message. In addition to this unique identification feature, the token message generator 53 also provides
The NATIONADDRE8s segment contains the contents of the succeeding node address register 51 and the S
The contents of the node address register 42 are included as the OURCEADDRESS segment. The communication protocols discussed here impose a specific time limit on the period during which a master node remains active. The time interval ζ is included in a timer 52 and is set to a predetermined value when a token acknowledge message is sent by a token acknowledge message generator 54. In this preferred embodiment, this time is set to less than 1 second. After the nine time interval set by timer 52 has elapsed, token message generator 53 is enabled and
The token message is sent to the communications ink 7ace 40, and the communications interface 40 places the token message on the data bus. In general, only master nodes that are active can transmit over the data bus, so under normal circumstances there should not be "collisions" between token messages and other messages. Less than 9% of the time, means are provided for handling collisions in a controlled situation, and these means are briefly described below.

The token acknowledgment message described above in connection with comparison element 46 is generated by token acknowledgment message generator 54 in response to a token message sent to master node 12, etc., which includes comparison element 46 as a part. Published by. The token acknowledgment message is the first thing a node sends when the maid becomes active in response to a token message. The MESSAGE TYPE segment of this token acknowledgment message incorporates a unique identification format that clearly distinguishes the token acknowledgment message from any other type of message. The generation of the token specification response message by the token acknowledgment message generator 54 includes:
This is facilitated by the comparison element 46 determining that the node address and the token message successor node address are equal. The token acknowledgment message includes the contents of the node address register 42 in its SOURCE ADDRESS segment. The Token Acknowledgment Message is sent by a node as a slave. The node will not take over as the active master until the sending master confirms that it correctly heard the token acknowledgment message. If no message appears during the allowed retry time, it indicates that the sending master has opened a token acknowledgment. After the retry time has elapsed, the master enables transmit activity 61. The token message from the token message generator 53 is the last message sent to the master node during the active period before the master node 12, etc. becomes inactive.

A token acknowledgment message transmitted over the data bus is received by the master that sends the token message, and the master transfers the token acknowledgment message to its token acknowledgment message register 44.
to be memorized. The master node's token acknowledge message register 44 then stores the next network address as part of the token acknowledge message in the node address register 42 of any master node 12, etc. that sent that particular token acknowledge message. will be included. This network address is transmitted to comparison element 48 where it is compared with the contents of successor node address register 51. Comparator element 48 detects that the addresses are not equal to each other.
The output path of carries the signal. In this case, unequal addresses essentially means that a master node other than the next to gain activity in the channel after the current master node aborts its activity as specified by the active master list actually receives the token. Indicates that the message is received. In this case, the active master list update flag register 58
is set. activity master list at a later point} (A
ML) The AML update flag that was sent when the update prompt message was sent is
Regardless of whether or not the sending of AML update messages is enabled, the mere appearance of a token acknowledge message indicates the provision of a token to any successor master node, and that node will 57 instructions.

Also, in rare cases, for a sent token message,
It is possible that the expected token acknowledgment message response may not be obtained. Most often this happens simply when no token acknowledgment message is provided. In this case, using the transmission of the token message from the token message generator 53, the timer 4
Operate 9. A timer 49 causes a timer 49 to run after a sufficient period of time has elapsed to assume that the node does not respond to the token message with a token acknowledgment message.
It is arranged to provide an input to the token message generator 53 that facilitates generation of another token message. In this case, the token message generator 53 typically uses the next address listed in AMLo to select the next node to send the token message to. If the AML is not stored, the master must find a master that will accept the token by sequential search. When a token acknowledge message occurs, whether correct or not, from the token acknowledge message register 44:
to timer 49, disable timer 49,
A signal is sent that prevents timer 49 from enabling further generation of token messages by token message generator 53.

One of the important aspects of the invention is a procedure that allows individual master nodes to be easily and efficiently added to the network, as well as allowing individual master nodes to be easily and efficiently added to and removed from the network. . One element that assists this activity is the activity master list} (
AML) update flag register 58. AML update flag register 58 contains an AML update flag that is set when the particular associated master node is activated. This flag remains set until a signal is applied to the clear input terminal of register 58 that clears the AML update flag.

The clear signal for the AML update flag register 58 is
This is an affirmative result of the comparison by the comparison element 46.

In addition, each card also has the ability to process another type of message with a unique identification format in the MESSAGE TYPE segment, which
This is an L update timing message. This message is sent in response to a command from one element of the communications master 16 while the communications master 16 is active with token e, and is received by the communications interfaces 40 of all other master nodes, respectively. AM of the corresponding node
It is sent to the L update inquiry message register 59. Each AML update interval message is sent to its SOURC
The E ADDRESS segment contains the network address of the next communication master 16 sending the message. When the node receives the respective AML update interim message, the AML update message generator element 6
2 is the DESTINATION of the transfer source address stored in the AML update time message register 59.
Generates an AML update message to be included as an ADDRESS segment. However, the AML Update Message Generator 62 will not function unless the AML Update Flag in the AML Update Flag Register 58 is set, i.e.
If this flag is not in its initial state at power-up or set when an incorrect token acknowledgment message is received,
Update messages are not transmitted through the communication interface 40.

It is possible that two or more master nodes may have their AML Ififr message generators 62 operating at the same time. Rectangle 41
The communication master function shown in 19 must be resolved. Although conflict resolution is beyond the scope of the present invention, it is possible to resolve message conflicts so that each master node can ultimately transmit AML update messages without causing a conflict. It's important to understand. This was also mentioned earlier. This concludes the explanation of the common master node function.

In order to fully understand the present invention, it is necessary to understand the special functions of the communication master node 16 contained within the rectangle 41 and the interrelationship between the common master node function and the communication master node function. This is very important. As mentioned above in connection with the description of instruction memory element 26 of FIG.
There are two main types of communication master functions to which the present invention pertains. These are the AML broadcast communication function and the AML update function.

The communication master node 16 communicates with other master nodes 1
2.13, etc., and are bound by the same protocols. That is, a communicating master node 16 may only transmit over the data bus when it is receiving additional token messages transmitted from another master node. The special case of designating the first active node at network power-up is irrelevant here. When the communication master node 16 becomes active, it periodically sends an AML Update Interim message as indicated to the AML Update Interim Message Generator element T3 under the control of a timer T2. In this case as well, each AML update interim message is
It has a unique identification format within the SAGE TYPE segment that identifies the AML Update Interim Message as a message of such nature, and the SOURCE A
The DDRESS segment contains the contents of its own node address register 42. The AML update timing message generator element 73 generates the master timing message D.
ESTINATION ADDRESS segments can be set to send these messages to one or a group of master nodes that have node address registers 42 specified for that segment. Each AML Update Interim Message is received by an AML Update Interim Message Register 59 in another node of the network, as described above and as follows, and the activities described in connection therewith This is executed if the receiving node has in its node address register 42 one of the values specified for the destination address in the AML update interim message address register 59.

A distinguishable A in response to an AML update interval message
When the ML update message is provided to the communication interface 40 via the data bus, the AML update message is sent to the AML update message register 71. A
The appearance of ML update messages means that either a new master node has been physically added to the network and token messages must be sent to it frequently, or there is a malfunction in the network. Therefore, it indicates that it must be inserted (re-) into that address t-AML.

Accordingly, AML updater element 70 receives the address value of the SOURCE ADDRESS segment located in AML update message register 71. This address is.
This is the node address of the master node 12, etc. that sent the AML update message. AML updater Shiko 70 inserts this address into AML fixed file 68. Also, in connection with this, there is a function to delete a node from AML, and this function will be briefly explained below.

An important aspect of the invention already mentioned relates to the means, internal to each master node 12, etc., for storing the correct address in the successor node address register 51. One element of this functionality is the AML broadcast generator 67.
This is done by adding AML to every master node in the system when a change occurs in AML.
The entire AML of the message is broadcasted respectively.

The AML temporary file 45 and the AML processor 50 which encodes and provides the next signal the correct address for storage in the successor node address register 51 have been described above. The AML broadcast generator element 67 in the master node acting as a communication master sends the individual network addresses stored in the AML temporary file 45 in each of the master nodes 12, etc.
This is Isono to be deleted from the persistent file element 68. For several reasons, such as power failure, node malfunction, removal, break in conductor 10 or 11, an individual node may not be able to respond to the sent token message. What has been said regarding the timer 49 and its interaction with the token message generator element 53 remains applicable in this case as well. A robust method would be to leave some leeway and allow a mask node to set its node address to DESTINATION ADDRESS
The network address and the associated master node lm should not be left out until several consecutive instances occur in which the token message contained in the segment does not respond. Therefore, communication master node 1
6 includes an AML that receives the contents of the token message register 43 and the comparison signal from the comparison element 46;
A counter control section 63 is provided. The AML counter control 63 is directly coupled to the AML counter file 64, which is stored as part of the data memo +7 2 0 (see FIG. 2). Each AML entry has its own counter in the AML counter file 64. The steps are as follows. The comparison signal from the comparison element 46 indicating that the communication master node 16 is active is received by the AML counter control unit 63, and the comparison signal is received by the AML counter control unit 63K! l
．． Serves as a counter decrement signal that decrements all counters in the AML counter file 64 associated with the active master node. Because the content of any one of the counters in the counter file 64 is decremented by the AML counter control unit 63,
Upon reaching zero, counter test element 65 provides the identification attribute of its master node. That is, test element 6
5 includes the node address in the absent master signal and transmits it to the AML updater 70. Therefore, AML updater 7
0 deletes the node address from the AML fixed file 68. As mentioned above, AML fixed file 68
Every time the AML updater 70K is changed, the updater 7
The update signal from 0 is sent to the AML broadcast generator 67 the next time the communications master node 16 becomes active.
ML Causes broadcast messages to be sent. This results in
Each master node in the network can update its successor node address register 51 in the same manner as when adding a master node to the AML.

In many cases, it will be found that only a few, perhaps only one, of the various master node successor address registers 51 in the network that require updating will need to be updated. However, the amount of time this procedure takes is not critical, as this is a relatively rare event once the system is properly installed and put into use.

AML counter control 63 has further functionality that applies to individual master nodes and entries in those master nodes' AML counter files 64. Each time a token message is received in the token message register 43, the source address in the message is retrieved by the AML counter controller 63, and the counter associated with that address in the AML entry in the AML counter file 64 is is reset to the value of The preferred value in the present invention is 4, but any number from 1 to possibly 10 can be used instead. Whenever a ditoken message is sent to a master node, it is implied that the master node was active. If the master node is active, its network address should be kept in AML. A master node should be removed from the AML stored in the AML fixed file element 68 if no token messages are generated by the particular master node during a certain number of token message cycles through the network. Only when

easily removed from the network without
You can see that it can be deleted. Each master node in the network has a system, for example, I{V
If widely distributed among the various devices to be controlled throughout the AC system, it is possible, for example, that a large number of different circuit breakers will be involved in supplying power to the various master nodes. If one or some of the nodes ceases operation, the network will still continue to function, albeit at a reduced capacity. If one mask node in the network fails and the entire system fails, the reliability and benefits of the control communication network will suffer considerably.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a typical communication network related to the invention described herein, FIG. 2 is a schematic block diagram of one of the maids in FIG. FIG. 4 is a diagram illustrating the structure of a message transmitted over a network. FIG. 4 is a detailed functional block diagram of the node in FIG. 10, 11...Conducting wire, 12,13.14.15...Master node, 16...Communication master node, 42...Node address register, 51...
...Successor Node Address Register, 67...Activity Master List Broadcast Message Generator, 68...
Activity master list fixed file. Patent Applicant Honeywell Incorporated Sub-Agent Masaki YamakawaFig. 3

Claims (1)

Claims: A plurality of master nodes all connected to a single data bus consisting of a pair of electrical conductors, each node containing a node address preassigned to that node. includes a node address register, and each node is of a type having an active mode such that the node supplies a plurality of different messages on the data bus consisting of electrical signals for communicating with other nodes. , each of said nodes includes a dedicated successor node address register for storing a network address different from the contents of the node address register, said active mode of one node has a predetermined unique identification format, and In response to receiving a signal over the data bus encoding a token message containing a successor node address equal to the contents of the node address register of that node, each of said nodes receives a successor node address of that node. further transmitting a token message containing a successor node address comprising the address stored in the register and terminating the active mode in response to receiving a token acknowledgment signal over the data bus having a predetermined unique format. , a first of the master nodes includes an address memory in which is stored an active master list containing the contents of the node address registers of the active master nodes in the network, the active master list including the nodes included therein. In a communication network which further specifies successor node addresses for each of the addresses: a) an active master list located in a first of the master nodes, having a predetermined unique identification format and stored in the address memory; b) active master list broadcast communication means for providing a signal on the data bus encoding an active master list message comprising at least a portion of the data; means for receiving an active master list message via a bus, and at each master node, responsive to the active master list message identification format, and from subsequent nodes specified in the active master list with respect to the network address of the associated master node; A communication network characterized in that it comprises means for retrieving an address and means in each master node for storing the network address so retrieved in a successor node address register of the associated master node.